Power line communication (PLC) is a general designation of all technologies in which power lines are used as communication channels. A PLC communication system transmits data via modulated communication signals on existing power lines, and the power lines are also used to supply power to residences, buildings and other places. In this case, the communication devices can be networked without newly added wires or cables. This feature is widely used in various applications, since a higher efficiency is obtained by taking full advantage of the network. Generally, the PLC technology is applied to public utility meters, home local area networks, household appliances and illumination control.
A unidirectional output power design is adopted in the power lines so far, and the transmission environment for communication signal propagation is severe. It is observed in narrow band power line communication (NB-PLC) that power line noise is a key factor resulting in a severe propagation environment. Typical sources of the PLC noise include: switching power supply, silicon controlled rectifier, commutator motor, dimming switch, and industrial source directly connected to supply network.
In order to improve the reliability of meter reading technology, a wireless communication technology may be adopted instead of the PLC. However, for the wireless communication technology, even in case of close physical distance, it is still difficult for communication devices in some regions to perform the wireless communication normally. For example, some obstacles in the basement of a building may block or weaken the radio wave, which makes it difficult to ensure the quality of the wireless communication.